07-09-2012, 11:55 AM
Wireless Communication in Process Automation
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ABSTRACT
The advancements in wireless networking technology, specifically in the short-range wireless
networking technology, offer an enormous opportunity for wireless connectivity of field devices both in oil and gas and other chemical processing plants. The prerequisite of a field network includes real-time support for mixed traffic, availability, security, reliability and scalability in a harsh industrial environment. These conditions have to be fulfilled by any wireless network in order to operate.
Previously, wireless solutions were not viable and preferred choice for offshore monitoring in Oil and Gas sector for many reasons like – Emerging, Non-robust and Immature technology, Security concerns, Incomplete or conflicting Standards, and clashing wireless frequencies and communications protocols.
This paper presents a brief overview of the requirements for wireless in process automation, relative standings of existing short-range wireless network technologies based on the outlined criteria, and associated short comings.
INTRODUCTION
The evolution in wireless technologies has opened the door to a new class of plant automation architecture that offers adopters a significant strategic advantage. Driven by substantial and measurable cost savings in engineering, installation, and logistics, as well as dramatic improvements in the frequency and reliability of field data collection, automation experts and IT professionals are presented with an opportunity to deliver a major, positive impact to the bottom line.
WIRELESS COMMUNICATION TECHNOLOGIES
Wireless technologies are often categorised based on thecoverage they offer, which ranges from meters to several kilometres.The range requirement is application dependent, for instance the requirements for wireless coverage in factory automation is relatively low compared to process automation.
Figure 1 provides an overview of different wireless networks, their associated standards and properties. Figure 1 has three axes: range (distance between communicating devices), transmit power (output power level of transmitter) and channel rate (speed of communication). At an enterprise level, the use of external resources like satellite and fixed telephony can be used for long range communications, whereas within the industrial environment, technologies covering WPAN and WLAN are of wider interest. In these regions the communication range is up to 100m and the transmit power allowance is low, but the data rate depends on the technology being used as can be seen in figure 1. Fig.1. Illustration of wireless network technologies based on channel rate, transmit power and range.
WORKING
In a wireless local area network, a device called an Access Point (AP) connects computers to the network. The access point has a small antenna attached to it, which allows it to transmit data back and forth over radio signals. With an indoor access point as seen in the picture, the signal can travel up to 300 feet. With an outdoor access point the signal can reach out up to 30 miles to serve places like manufacturing plants, industrial locations, college and high school campuses, airports, golf courses, and many other outdoor venues.
In a wireless local area network, a device called an Access Point (AP) connects computers to the network. The access point has a small antenna attached to it, which allows it to transmit data back and forth over radio signals. With an indoor access point as seen in the picture, the signal can travel up to 300 feet. With an outdoor access point the signal can reach out up to 30 miles to serve places like manufacturing plants, industrial locations, college and high school campuses, airports, golf courses, and many other outdoor venues.
CONCLUSION
Wireless technology holds enormous potential for the process industry to meet their rising demands while maximizing potential at reduced cost with less constrained infrastructure. The requirements at field level are stringent compared to higher levels of the automation hierarchy; nevertheless they are achievable. It can be summarised that the short-range and low-power wireless communication technologies are safe for process automation applications. The challenges and concerns regarding interference and jamming are being addressed by industry using schemes like channel hopping and frequency agility. The two new standards, wireless HART and ISA100.11a are both well positioned to address the industrial needs especially because of the advance security, channel hopping, TDMA and blacklist-based approach to guarantee real-time operations and reliability in an unprotected licence-free radio spectrum.